There were some attempts made recently to provide stairclimbing devices of different kinds which might be used for carrying up- and downstairs various objects, either heavy, or inconvenient in handling.
One collapsable shopping cart construction (U.S. Pat. No. 4,722,538) employs a combination of a movable and immovable frames, pivotably connected to each other by means of a pair of diagonal links. In an upright position the construction is supported by a pair of braces incorporated with a crossbar, slidably positioned over the vertical rear legs of the cart.
This type of construction, although reliable and sturdy, appeared rather costly in production and complicated in operation. Besides, the braces, the crossbar and diagonal links all together create considerable extra weight, which is not desirable in a shopping cart.